This article describes a concept and methodology for the modelling of compact
heat exchangers with arbitrary flow arrangement. The new model enables
integrated virtual testing including simulation of thermal and hydraulic
performance, cavitation behavior, and thermal structural stresses. In order to
limit the calculation cost, the problem solving is split into two steps: firstly the
CFD turbulator characteristics will be determined with very fine geometric
resolution for the heat transfer surface related micro physics; secondly the global
CFD conjugate heat transfer will be calculated with a coarse mesh by use of the
porous media concept. A key issue in the second step is the representation of
the turbulator characteristics which are dependent on the arbitrary flow direction
and the local Reynolds and Prandtl numbers. Unlike a usual porous media
approach in which the turbulator solid is replaced, the global flow and heat
transfer calculation is carried out here by use of the user-developed coding and
the StarCCM+/StarCD model of conjugate heat transfer in anisotropic porous
media. With the calculated temperature distribution in the structure used
as loading, a thermal stress analysis can be performed to evaluate the
thermo-mechanic fatigue life of heat exchangers. Measurement shows that the
predicted heat transfer performance and the pressure losses with the described
multi-scale calculation strategy compares well with the experimental data with a
maximum deviation of about 10%.
Keywords: liquid to liquid heat exchanger, multi scale calculation, turbulator
properties in arbitrary flow direction, conjugate heat transfer in anisotropic
porous media, thermal and hydraulic characteristics, thermal structural stresses,
heat exchanger model, cavitation identification, CFD calculation, experimental
validation.